master branch: commit r15-4198 failed to bootstrap on Linux/x86_64 (commit r15-4186 builds)!

[haochenj--- via Gcc-testresults]

make[2]: Entering directory '/export/home/haochenj/src/gcc-regression'
rm -rf bld
mkdir -p bld
cd bld; \
RUNTESTFLAGS="--target_board='unix{-m32,}'" ../src-master/configure \
        --with-arch=corei7 --with-cpu=corei7 --enable-clocale=gnu 
--with-system-zlib --enable-shared --enable-cet --with-demangler-in-ld 
--enable-libmpx --prefix=/usr/gcc-15.0.0 --with-fpmath=sse 
checking build system type... x86_64-pc-linux-gnu
    grep -E "(error:|Error)" makelog.r15-4198.x86_64.corei7 >> 
makelog.r15-4198.x86_64.corei7.mail; \
    tail -n +20 makelog.r15-4198.x86_64.corei7 | grep -C 10 -E "error:|Error:" 
>> makelog.r15-4198.x86_64.corei7.mail; \
make[6]: [Makefile:1832: x86_64-pc-linux-gnu/bits/largefile-config.h] Error 1 
(ignored)
make[6]: [Makefile:1831: x86_64-pc-linux-gnu/bits/largefile-config.h] Error 1 
(ignored)
make[6]: [Makefile:1832: x86_64-pc-linux-gnu/bits/largefile-config.h] Error 1 
(ignored)
../../src-master/libcpp/directives.cc:2078:20: error: unknown conversion type 
character ‘<’ in format [-Werror=format=]
../../src-master/libcpp/directives.cc:2078:34: error: unknown conversion type 
character ‘>’ in format [-Werror=format=]
make[6]: *** [Makefile:227: directives.o] Error 1
make[5]: *** [Makefile:12975: all-stage2-libcpp] Error 2
make[4]: *** [Makefile:30028: stage2-bubble] Error 2
make[3]: *** [Makefile:30272: bootstrap] Error 2
make[2]: *** [Makefile:313: bootstrap] Error 2
==================== Detailed Info around error (+- 10 Lines) 
====================
4 translated messages, 86 fuzzy translations, 184 untranslated messages.
ok
checking for sysroot... no
checking for a working dd... /bin/dd
checking how to truncate binary pipes... /bin/dd bs=4096 count=1
checking for x86_64-pc-linux-gnu-mt... no
checking for mt... no
checking if : is a manifest tool... no
checking how to run the C preprocessor...  
/export/home/haochenj/src/gcc-regression/bld/./prev-gcc/xgcc 
-B/export/home/haochenj/src/gcc-regression/bld/./prev-gcc/ 
-B/usr/gcc-15.0.0/x86_64-pc-linux-gnu/bin/ 
-B/usr/gcc-15.0.0/x86_64-pc-linux-gnu/bin/ 
-B/usr/gcc-15.0.0/x86_64-pc-linux-gnu/lib/ -isystem 
/usr/gcc-15.0.0/x86_64-pc-linux-gnu/include -isystem 
/usr/gcc-15.0.0/x86_64-pc-linux-gnu/sys-include   -fno-checking -E
../../src-master/libcpp/directives.cc: In function ‘void 
do_pragma_once(cpp_reader*)’:
../../src-master/libcpp/directives.cc:2078:20: error: unknown conversion type 
character ‘<’ in format [-Werror=format=]
 2078 |                  "%<#pragma once%> in main file");
      |                    ^
../../src-master/libcpp/directives.cc:2078:34: error: unknown conversion type 
character ‘>’ in format [-Werror=format=]
 2078 |                  "%<#pragma once%> in main file");
      |                                  ^
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes